FiKure 1. — Five (^eoeraphic areas of the northwest Atlantic com- 

 posing the sampling area Tor Tish food studies, 1969-72. 



>20 cm; red hake, Urophycis chuss (Walbaum), >20 cm; 

 white hake, Urophycis tenuis (Mitchill), >20 cm; spot- 

 ted hake, Urophycis regius (Walbaum), >10 cm; longfin 

 hake, Phycis chesteri Goode and Bean, >10 cm; offshore 

 hake, Merluccius albidus (Mitchill), >20 cm; fourbeard 

 rockling, Enchelyopus cimbrius (Linnaeus), >10 cm; 

 cusk, Brosme brosme (Miiller), >20 cm; marlin-spike, 

 Nezumia bairdi (Goode and Bean), >10 cm; longnose 

 grenadier, Coelorhynchus carminatus ((ioode), >10 cm; 

 fawn cusk-eel, Lepophidium ceruinum (Goode and 

 Bean), >10 cm; and the ocean pout, Macrozoarces 

 amencanus (Bloch and Schneider), >10 cm. 



In the laboratory, the preserved stomachs were opened 

 and the contents emptied onto a fine mesh screen to per- 



mit washing without losing any food items. The vauious 

 prey item« were manually sorted, identified to the low- 

 est possible taxa (using a dissecting microscope when 

 necessary), and damp dried on bibulous paper. Each 

 taxonomically distinct group was weighed to the nearest 

 0.01 g on a Mettler balance, immediately after blotting. 

 Parasites in the stomach were included as part of the 

 stomach contents and are incorf)orated in the tables un- 

 der "Other Groups." 



Food 



The food of each species of fish is summarized on a 

 weight basis as a percentage of the total weight of stom- 

 ach contents. In the tables the subtotals for the major 

 prey categories, i.e., subtotals for the major taxa, are off- 

 set and italicized. The tables follow a standard format to 

 facilitate comparison of the food between species. In the 

 text the broader groupings of prey, as presented in the 

 tables, are discussed in detail. The percentage weight is 

 included in parentheses after the first mention of a prey 

 group in order to quantify that particular prey's signifi- 

 cance in the diet at that taxonomic level. 



Dietary Overlap 



Percentage similarity, as a measure of dietary over- 

 lap, was calculated according to the formula of Shorygin 

 (Ivlev 1961) as follows: 



P.S. = 100-0.52 1 a-6 1 



or, more simply, by summing the smaller value, in this 

 case the percentage weight, for all prey shared by the two 

 predators. Accordingly: 



P.S. = 2 min (a,b) 



where: P.S. = percent similarity 



a = percentage weight for a given prey 



group for predator A 

 b = percentage weight of the same prey 

 group for predator B. 



If a +, indicating <0.1''r weight, was the smallest 

 value for any prey group in the table it was arbitrarily as- 

 signed a value equal to 0.05'^c for the calculations. 



RESULTS 



Food 



Since the data are presented as percentages it is 

 possible to compare the food of each species directly and 

 independently of the sample size. A detailed comparison 

 of food between species will be made later but first we 

 consider separately the food of each species over the en- 

 tire study area (Table 1, Fig. 2) and then by the geo- 

 graphic areas (remaining tables) shown in Figure 1. 



